There were few studies on benzothiazine derivatives useful as therapeutic drugs. Especially, there is only one prior publication, Japanese Unexamined Patent Publication No. 148771/84 filed by the same inventors of this invention, disclosing the compounds useful for treatment of circulatory diseases of the present object. The inventors further advanced the previous study to find out novel and useful compounds. The characteristic of the chemical structure of the compounds of this invention is that phenyl group substituted at 2-position of benzothiazine ring has a side chain which has a substituted or unsubstituted phenyloxy group. Such structural characteristic has not been disclosed in the above Japanese Unexamined Patent Publication No. 148771/84.
As other prior arts concerning compounds having benzothiazine ring, there exists publications by J. Krapcho (U.S. Pat. No. 3166554), Stearns et al. (U.S. Pat. No. 3,555,155) and Stanley O. et al. (Can. Pat. No. 717979). The chemical structures of the compounds disclosed in the respective patents are different from those of this invention and the objects thereof are also different. The object of the patent of J. Krapcho is a treatment of Parkinsonism, the patent of Stearns et al. is on herbicides, and the patent of Stanley et al. is on medicines having anticholinergic activity and antihistaminic activity.
The object of this invention is to search and find more useful drugs for circulatory diseases based on the prior arts.